Can medical marijuana treat epilepsy?

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How do drugs like Epidiolex work, and who might they help? Hannah Cock, Professor of Epilepsy at St George’s in London, joined Chris Smith in the studio.

Hannah - Epilepsy is not one disorder, it’s hundreds and hundreds of different types of disorder but, essentially, it’s a disorder of the brain characterised by recurrent unprovoked seizures and by a range of associated biological, sociological, and psychological consequences. So things like memory problems, difficulty functioning, anxiety, and so on. There’s an enormous spectrum from people who are, essentially, 100 percent normal other than for the few minutes when they have their seizures to people with much more complex and very frequent events.

Chris - What about the mechanism of their epilepsy that means it might be amenable to being managed with cannabis?

Hannah - I don’t think we know the answer to that question yet. With respect to Epidiolex or indeed any other drug, the drugs are being tried in particular rare syndromes at the moment but that doesn’t mean that the drug won’t prove to be effective in other types of epilepsy in the future.

Chris - Do we have any idea as to what it might be doing to the nervous system in order to make the seizures less serious? Do we understand actually how it influences epilepsy when people use these agents?

Hannah - With respect to cannabidiol which is the CBD, which is the one that’s been best studied rather than THC, we don’t know how it works in epilepsy. It doesn't seem to be by the CB1 and CB2 receptors that were mentioned earlier. It might be affecting some of the brain’s own mechanisms that stop seizures being there all of the time. Most people with epilepsy aren’t fitting 100 percent of the time. We have our own internal switch that stops seizures so there’s a lot of interest that it might be influencing that, but we don’t really know.

Chris - I wondered if because people are swallowing this whether rather than it going into the brain and having an effect, it might be influencing perhaps the bacteria in the intestine - the microbiome, the nervous system that supplies the intestine - therefore other parts of how the body is working and that in turn is having a knock-on effect which is having benefits of how the brain responds?

Hannah - There’s absolutely no evidence to support that. Epilepsy is a disorder of the brain and actually these drugs they’re very very fat soluble and so they do penetrate the brain very readily even when you swallow them.

Chris - What might be the long term consequences for someone who uses one of these cannabis-like agents if they treat their epilepsy with it, because they’re going to be doing that chronically for a long period of time aren’t they?

Hannah - Yeah. And I think with respect to the agents that contain THC we do know that long term use is associated with problems. With damage to memory and thinking, to mental health and brain structure, particularly in children who seem to be very vulnerable to this. With cannabidiol, that’s why doctors and scientists have focused so much on cannabidiol rather than the THC components. And we don’t yet know what the long term consequences might be because these are relatively new trials and that people have been taking them, some people for up to a few years. But we don’t know what the long term consequences might be yet.

Chris - It’s rather worrying to me that we’re considering changing the law and perhaps allowing people to try these agents, admittedly in people with severe disabling epilepsy, when we don’t actually know how they work.

Hannah - Any new drug, any advance in medicine, there’s always a degree of uncertainty when it’s first licenced and first available because, by definition, there won’t have been decades of evidence. And that’s why it’s so important that if people do take these drugs it’s part of a well regulated controlled study, and with the knowledge of the health professionals so that we can monitor in the long term what the side effects might be.

We do also know that even in the short term there’s a bit of an urban myth that these drugs don’t have side effects - they do. One in three people in the studies who took cannabidiol did have side effects like diarrhea, reduced appetite and vomiting, and in about 1 in 23 people, there were quite serious side effects. So it’s not that these are blanket safe, much better than existing drugs. We don’t know that yet.Chris - So not to be taken lightly. Thank you Hannah Cock, St George’s, University of London.

Izzie - So the take home message is, yes, there is truth in the idea that cannabis-based products have medicinal value in some cases for some medical conditions. But on the flip side, there is still a whole lot we don’t know about it.